As you have learnt in Section 1, there are two types of malnutrition – acute and chronic. In this section, we will focus on acute malnutrition. Acute malnutrition can be classified as moderate or severe. In order to understand this classification and to determine how severely a child is malnourished, you need to know about the WHO growth standards and the term Standard Deviation (SD). Let’s check your understanding about SD first. Describe what SD is and how you can use it to determine the severity of acute malnutrition in relation to the indices you should use.